The Precipitation Regulation Of NaYF 4 /NaGdF 4 Nanocrystals In Glass-ceramics Enhances The Up-conversion Luminescence Properties Of Er 3+

Upconversion luminescence materials with rare earth doped have been the focus of research all over the world.The reason is that these materials have important potential applications in the field of fluorescence display.Oxyfluoride glass ceramics have good mechanical properties of oxide glass,and they also contain the advantages of fluoride nanocrystals with low phonon energy environment.Therefore,oxyfluoride glass ceramics are excellent upconversion materials with high optical transmittance,high rare earth ion solubility and low phonon energy.This paper has studied the relationship between glass components,network structure and the crystallization of glass,and also discussed the effect of glass network structure on upconversion luminescence with Er³⁺ rare earth ions doped.?1?The effect of component regulation on the activation energy of crystallization in glass ceramics was investigated.The grain size of NaYF₄ crystallites in oxyfluoride glass ceramics doped with Er³⁺ ions was controlled by changing the activation energy of crystallization.When the content of NaF in glass component is more,the integrity of glass network structure can be reduced and the crystallization activation energy of glass sample is reduced.?2?The influence of crystal type on upconversion luminescence of Er³⁺ ions was investigated.Solid solution Na(Y_1-x,Gdx)F₄ microcrystals have been successfully precipitated in glass samples.In glass,when the dopant concentration of GdF₃ is increased,the crystal type in the glass was changed from NaYF₄ to Na(Yi_1-x,Gd_x)F₄,and finally to NaGdF₄ crystal.The fluorescence emission intensity of Er³⁺ ions increases.This is because the atomic radius of Er is closer to Gd than Y,which facilitates more Er³⁺ ions to enter the lower phonon environment of nanocrystals,and enhances the upconversion luminescence of Er³⁺ ions.?3?The influence of crystal size on upconversion luminescence of Er³⁺ ion was investigated.The glass samples were synthesized with LiR lithium halide?R=Br,Cl,F?doped,Br-,Cl-and F-electronegativity has gradually increased.The formation of chemical bonds between lithium halide and glass network were changed gradually by covalent bonds into ionic bond,which is beneficial to the precipitation process of crystal.Therefore,the size of precipitated NaGdF₄ nanocrystals have been controlled.In addition,as the grain size increases,the upconversion luminescence of Er³⁺ ions increases gradually.?4?The influence of crystal symmetry on upconversion luminescence of Er³⁺ ions was investigated.The Li₂CO₃ can make the main micro structural units in glass change from low to high,which destroyed the integrity of glass network structure and enhanced the crystallization ability of glass.Therefore,the grain size of glass ceramics were increased with more Li₂CO₃ doped and the intensity of upconversion luminescence is enhanced.Small size Li+ ions also lead to crystal lattice distortion of NaGdF₄ nanocrystals,which reduced the cross relaxation process between Er³⁺ions,The green fluorescence emission process of Er³⁺ ions was enhanced.